A series of 4-substituted-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidine derivatives (4a-f) were prepared by the displacement reaction between various amines and 4-chloro-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidine (3). The structure of the compounds has been established on their analytical and spectral data. All the compounds have been screened for antihyperlipidemic and antimicrobial activities. The compounds 4c and 4d showed good antihyperlipidemic activity in reducing serum cholesterol level when compared with standard, gemfibrozil. Compounds 4a and 4d were found to have excellent antimicrobial activity against Staphylococcus aureus and Streptococcus pneumoniae when compared with standard used (amoxicillin-clavulanic acid).